Carrier-wave telephony over power lines



June 24, 1930. c. A. BOPDIE 1,765,480

CARRIER WAVE TELEPHONY OVER POWERLINES I Allyn-4n INVENTORI g l Clarence 17'. BOdd/t E BY WTTORNEY June 24, 1.930. c. A. BODDIE CARRIER WAVE TELEPHONY OVER rowan LINES Filed Oct. 24, 1923 4 Sheets-Sheet 2 m ME INVENTOR C/are/Ice 500d/e ATTORNEY WITNESSES:

Jim? 24, 1930. c BODDIE 1,765,480

CARRIER WAVE TELEPHONY OVER POWER LINES Filed Oct. 24, 1925 4 Sheets-Sheet 3 Q E g S x ti 1 NTEF M cn Q Q O N m g \o N m N S g T 3' $3 j o m r Q m m "3 Q N a i dag WITNESSES: INVENTOR Clarence H fiodd/e.

' t g 7 BY W ATTORNFY June 24, 1930.

c. A. Bonn":

CARRIER WAVE TELEPHONY OVER POWER LINES Filed Oct. 24, 1923 4 Sheets-Sheet '4 INVENTOR U/arenae l7 Budd/e.

ATTORNEY WITNESSES:

Patented June 24, 1930 UNITED STATES.

-PATENT OFFICE CLARENCE A. 'BODDIE, F PITTSBURGH, PENNSYLVANIA, ASSIGNO R TO WESTINGHOUSE same sending ELECTRIC & MANUFACTURING COMPANY, A

CORPORATION OF PENNSYLVANIA CARRIER-WAVE TELEPHONY OVER POWER LINES Application filed October 24, 1923. Serial No. 670,511.

This invention relates to communication by carrier-wave oscillations,either through space or along wires.

It is an object of this invention to use the and receiving apparatus both for communication and for the control of distant electromechanical devices, particularly for the control of distant station-selective means.

It is well known that radio-frequency oscillations may be modulated by superposing thereon a periodic change of amplitude. The radio-frequency thus modulated is often called the carrier wave and the modulation is frequently of audio frequency, for carrying telephone messages. Double modulation, by which the'carrier wave is made to convey two telephone messages at once, is also known. Control of electro-mechanical devices requires the changes in the radient energy to endure for periods corresponding to the time required by the electro-mechanical device to respond to the changes. These relatively slow changes will be herein called impulses.

If such impulses are produced by intermit tent sending and interruption of the carrier wave itself, the result is unsatisfactory because, even when a large amplification is used at radio frequency, there will not be current changes in the output circuit of the detecting device, large enough to makeit feasible to control a relay by the radio-frequency energy, and amplification at audio frequency cannot be had when no modulation having audio frequency is present..

It is an object of this invention to overcome this difiiculty and control electro-mechanical devices by radiated energy. If a modulation having audio frequency is imposed upon a radio-frequency carrier wave, the detector which receives this energy will give out an audio-frequency current. If such an audio-frequency current is'passed through a second detector, the output from the second detector can be used to control a relay. If amplification is needed, it can be performed at audio frequency and consequently there is no difficulty in obtainin in the output circuit, current changes 0 the size needed by the relay. This principle is employed to accomplish the object of this invention just stated. v

The-audio-frequency.modulation is superposed upon thecarrier wave, in impulses so that the first detector produces a succession of trains of audio-frequency oscillations. The length of each train corresponds to the time during which the audio frequency modulations are impressed upon the carrier wave, that is, to the length of one impulse. Such a train produces in the output of the second detector a succession of direct current im' pulses, each impulse enduring as long as the corresponding impulse of audio-frequency modulation of the carrier wave, which is as long as the corresponding train of oscillations in the output .of the first detector.

It is an object of this invention to make use of the method just explained forcontrolling station selectors or other distant electro-mechanical devices over a' system of sending and receiving apparatus that is also used for telephony.

As an incidental object, this invention pro-- duces a thermionic device with a changeable set of connections, so that it may servea lte'rnately as a generator of audio-frequency currents and as an amplifier for voice signals.

It is a further object of this invention to roduce a system of communication includmg a dispatchers station and a number of other stations, in which the dispatchers station may communicate at'any time with any of the other stations,.except one that is then engaged in conversation. This object of the invention is accomplished by means of provisions at each station, except the dispatchers station, for changing the fundamental carriervave frequencies at each of said stations.

Otherwise stated, this object of the invention includes so selecting the frequency for sending and the frequency for receiving, at each of the several stations, that any one station may readily place itself in that relation to the other stations which normally is characteristic of thedispatchers station. 7

Other objects and constructional details of the invention will be apparent from the following description and claims when read in Fig. 4 is a set of curves illustrating the waveforms employed.

Referring to Fig. 1, the apparatus for sending includes an antenna circuit 1 of the usual .form. A coupling 2 is provided between this circuit and a pair of vacuum devices 3 and 4 which have thewell known system of connections for the" sYT-call'd Heising or constant current production of modulated high frequency. No difference between the usual and familiar construction of these devices and the construction employed in-my invention is necessar but I have found it convenient to emp oy a source of alternating current 5 instead of a battery for the power for these tubes. A transformer 6 enables this source to supply low potential alternating current for heating the filaments, and a rectifier 7 enables it to supply high potential direct current for the plate circuits. sending apparatus is idle, the source 5 is dis engaged, ut' when the sending apparatus is being used, the source is connected thereto by the action of a relay, as will be explained below.

The rid circuit of the modulator tube .4 is couple by an audio-frequency transformer 8 to the-plate circuit of a vacuum tube 9. This tube is also energized fromthe source 5 in the same way as the other tubes. It is capable of two functions depending upon the position of the armature of the relay 11. When this armature is against its back stop, the'grid circuit of the tube 9 is connected to the secondary of the transformer 12. This circuit includes a grid biasing battery and goes to the filament through the divided resistor 10. When the armature is against its front contacts, the grid is connected to the coil 13 which is coupled with the plate circuit. From this coil, the grid connection passes through the same biasing battery to the filament. A condenser 14 is in shunt with the coil 13, and the 'coil 13 and the condenser 14 together form a circuit capable of oscillating ataudio frequency. When the relay 11 is energized, therefore, the tube 9 acts as a generator of audio-frequency currents which control the modulator tube 4 and thus produces an audiofrequency modulation of the radio-frequency output from the tube3. This output passes through the coupling 2 .to the antenna 1. If, therefore the relay. 11 is intermittently energized while the sending apparatus is working, the radiations from the antenna 1 will which is intermittently When the consist of the radio-frequency carrier wave modulated by impulsesof audio frequency.

When the relay 11 is de-energized and the grid circuit of the tube 9 includes the secondary12, voice signals may be impressed ,upon the grid by means of the telephone trans mitter 16, provided that the armature of the relay 17 is against'its front stop. The provisionsfor controlling this relay 17.will be explained below. While the potential of the grid of the tube 9 is controlled by the voice currents, the modulator tube 4 will be correspondingly influenced and the outputfrom' the antenna 1 will consist of the radio-frequency carrierwave modulated to correspond to the voice signals.

- The receiving apparatus shown in Fig. 2

includes an antenna 21 with the usual circuit connecting it to the ground. The coupling 22 associates thisantenna with the first detector tube 23. The connection to the grid of this tube includes a grid condenser 20 and a grid leak 30. The size of this con-, denser and leak are selected so that the first detector tube 23 will produce, in its output circuit, an audio-frequency current when the receiving energy is modulated by audio frequency, and a voice-signal current when the carrier wave is modulated by the voice signal. This output circuit is coupled by an audiofrequency transformer 24 to an amplifier 25. The output circuit of this amplifier is controlled by the contacts of the relay'26. When the armature of this relay is against its backstop, the output circuit of the amplifier 25 goes through the primary of an audio-frequency transformer 27. The secondary -of this transformer leads to thegrid of the s ec-.

ond detector tube 28. The'connection to this .grid includes a grid condenser 29 and a grid leak 31. The size of this condenser and leak are so chosen that the second detector tube 28 fis capable of rectifying the audio-frequency current which it receives. The plate circuit of the second detector tube 28 includes a relay 32. When the normal current is flowing in this plate circuit the armature of this relay is held away from itsback stop but, when audio-frequency, current arrives at the-transformer 27 so that the current in the plate circuit of the tube28 is diminished, the.

The output circuit of the amplifier tube 25, when the armature of 'the relay 26 is against its front stop, includes the primary of an audio-frequency transformer 33, 'the secondary of which is connected, by conduc- 'tors 34 and 35 to the telephone receiver 36 in Fig. 1. When the energy received upon the antenna 21 consists of the carrier wave, modulated by the voice signal, the first detector tube 23 will produce in itsoutput circuit an audio-frequency current whose amplitude varies in accordance with the Voice signal. This" current will be amplified by the tube 25 and will produce voice signal currents in the transformer 33 so that the Voice signal will be reproduced in the receiver 36.

Between the coupling 2 for the antenna 1, in Fig. 1,- and the antenna 21, in Fig. 2, there is connected a tuned circuit which is described at greater length in my co-pending application, Serial No. 658,041, filed August 18, 1923, which has since matured into Patent No. 1,673,548. The purpose of this connection between the sending and receiving antenna is to prevent the energy radiated by the antenna 1-from aifecting the receiving apparatus in its own station. The connection includes two conductors 40 and 37 which are united to the coupling coil 2 at points on;

opposite sides of the ground connection .38.

On Fig. 2 itmay be seen that the conductor 40 includes an adjustable resistor 39 and the conductor 37 an adjustable condenser 41. The conductors 40 and 37 are united together and to the antenna 21 as shown at 42.

When the operation of the system requires that the sending and receiving antennae have their constants changed, to establish communication with a selected station, the change at the sending station, is accomplished by the triple ole, double throw switch 43, Fig. 1, which 15 controlled by the relay 44, as will be explained below. 'When this switch is in the illustrated position, a certain portion of the inductance in the coupling 2 is included in the antenna circuit. When the switch is in the opposite position a smaller portion of the inductance 2 is included in the antenna circuit. The changes in the circuit of the antenna 21, in Fig. 2, are effected by a relay 45. When the armature of this relay 1s against its front stop, the supplementary condenser 46 is included in the antenna circuit in parallel with the usual tuning condenser; A similar change in the oscillating circuit associated with the coupling 22 is effected. by the relay 47. \Vhen the armature of this relay is against its front stop, the condenser 48 is connected in parallel to the condenser permanently in this oscillating circuit. When these changes are made, a corresponding change -is needed in the connection between thetwo antact, the condenser 51-is connected in parallel to the condenser 41, already described.

The connections and arrangement of the several relays will be best explained in connection with a description of the operation of the system. This will first be given for two stations each equippedwith the apparatus illustrated in Fig. 1 and'Fig. 2 and the application to a system embodying more than two stations will be explained afterward.

Assume that all the parts are in the position illustrated in the drawings and that the operator at one station, hereinafter designated as the calling station, wishes to com municate with a certain station hereinafter named the called station. He first removes the telephone receiver 36 from its hook. This establishes a connection through the relay 53,

and establishes a connection from the battery 9 61, through the primary of the transformer 12, conductor 62, through the telephone transmitter 16 and conductor 57 to ground.' This places the telephone transmitter into condition for delivering voice currents where by the sending apparatus is now ready for voice signalling.

If the choice ofthe station with which the operator is to communicate requires that the constants ofhis antenna be changed the operator will correspondingly manipulate the dial 63. -This dial opens and closesthecircult a predetermined number of times,depending upon the manner in which the oper ator manipulates it. For changing the constants of the antenna, the operator causes the dial to close the circuit a number of times which does not correspond to the call for any station. In many systems, the dial closes the circuit from one to nine times for each digit in the call number ofthe desired station, leavng the digit zero, which corresponds to closmg the circuit ten times, for any special purpose. Assuming, therefore, that this method is used in the present case, the operator causes the dial 63 to close the circuit ten times. This results in the magnet 64 being energized ten timesfrom the battery 65 over conductors 66 and 67. The ratchet wheel controlled by the magnet 64 is thus rotated through ten spaces whichcauses contact to be made between the arm 68 and the terminal 69 and thus establishes a circuit from the battery 65, over conductor 71, arm 68, terminal 69 and 5 over conductors eondu ctor 72 to the relay 73. Energizing the latter relay causes the relay 44 to pick .up, be-

cause this relay is eznergized from the source The selector, including magnet 64 and the mechanism operated thereby, is shown only diagrammatically because its details form no part of the inventioncovered by this application. As is well known to those skilled in the automatic telephone art, afiter' the operation of the dial 63 has closed the circuit a predetermined nu'mberof times, the cessation of impulses from the dial permits the ratchet wheel and its arm to return to their'normal position. The relay 44 closes a shunt about the contacts of relay '7 3 and so remains energized after arm 68 and terminal-69 have separated. The rehiy 44, by closing the switch 75 establishes'a circuit from the battery 76 over conductors 78 and 79 torelays 45, 47 and v 49 in Fig. 2. The energization of the relays 45,47 and 49 connects the'condensers 46, 48 and 51 so that they add their capacities to the several circuits as alre'adydescribed.

It will be obvious that the connection be-. tween battery and conductor 72 could be established by a supplementary circuit closer instead of by a special manipulation of the dial63, ifdesired. It will also be obvious that instead of controlling the changes in the antenna 21 and its associated circuits by the relay 44, a key or dial forming part-of the receiving apparatus may be provided for this purpose. It will also be obvious that the closing-of the contact between arm 68 and terminal 69 may be performed by the operator either befor'eor after the telephone receiver '36 is removed from its hook.

After 'the receiver is removed from its hook, the operator can establish communica- 1 tion with a selected station by sending, by means of the dial 63, the requisite number of impulses. Each time that the dial 63 closes the circuit, the relay 11 is energized from the battery 81 over conductors 82,66 and 67 to ground. Thiscauses the vacuum tube 9 to generate audio-frequency. trains. The number and duration of .thcse trains correspond to the number and duration of the impulses sent out by the dial 63.. As explained above, this operation of the tube 9 causes the carrier wave 'to be intermittently modulated, the modulations being of audio frequency their duration constituting the impulses.

VVhen' this radiation is received at the called station, a corresponding current is produced in the'antenna 21 at that station.. This gives, in the output circuit of the first detector tube 23 there, a series of trains of audiofrequency oscillations, which are amplified by the'tube 25 andproduce in the second detector, series of diminntions, or negative impulses," in its output current. Consequently, the relay 32, at the called station, closes each time that dial 63 closes its circuit at the callpulses,

' through conductor88, the magnets 89 and ing station, and the duration of the closure of the relay 32 corresponds to the duration of the impulses from thedial.

Each time that the contacts of relay 32 close, a circuit is established from the conductor 7.9 over conductor 83 through the magnet 84 to the battery 85, returning over conductor 79. Thus the magnet 84, at the called station, is energized each time that the dial 63 at the calling station closes the circuit. This operates the ratchet wheel 85 and causes contact between the terminal 86 and the arm 87, when the requisite number of impulses have been sent. called station, will have their contacts corresponding 'to 86 and 87 closed either by a smaller or a larger number of impulses. If the closure atsaid other station corresponds to a smaller number of impulses, it will not produce any result, because it does not last long enough.- If the closure at the other station corresponds to a larger number of imit does not occur when the ,dial is manipulated for calling the desired station. lVhen the proper number of impulses has been sent and the arm 87 contacts with the terminal 86, it remains there until the release mechanism responds to the cessation of the impulses, andpermits the ratchet wheel '85 to return to its normal position. The mechanism by whichthis is'accomplished is familiar to those skilled in the art of automatic telephony and does not need to be described here The circuit established by the arm 87 is and 91 in parallel, and conductor 92 to the battery not open at the relay 17, because .it is the relay station. The energization of the relay 91establishes a holding-circuit for it and the relay S9. This circuit extends from the ground zit 93 through the rela s 91 and 89 in parallel and conductor 92 as before described. The energization of the relay 89 closesa circuit from the battery 94 over conductor 95 to the bell 96 and to ground. This causes the bell to ring and to continue to ring until the operator at the. called station removes the receiver 36, thus energizing the relay 17 at the called station and opening the connection between conductor 92 and battery 59. The energization of the relay 17 at the called station connects its telephone transmitter 16 to the transformer 12 and battery 61.

Lifting the receiver 36 also closes a connection from the ground through conductor 57, switch hook, conductor 97 and relay 26 to the battery 98. Energizing the relay 26 changes the connections of the amplifier tube 25 whereby, instead of the primary of the Stations, other than the It will 59. It should be noticed that this circuit is be impossible for any other station to call the called station-while the receiver 36 is off of its hook, because no energy can be transmitted from the amplifier 25 to the second detector 28. Including the primary of the transformer 33 in the output circuit of the amplifier 25 couples this output circuit to the tele phone receiver 36 so that conversationis now possible between the calling and the called station.

Referring to Fig. 4, the manner in which the impulses sent out by the dial 63 are translated into motions of the armature of the relay 32 will become clearer. The curve A in this figure represents the impulses sent out by the dial 63 and so represents the current in the relay 11. When this relay is energized,

the output circuit of the vacuum tube 9 delivers audio-frequency current, represented by the end portion of the curve B. When the relay is deenergized, no changes take place in the output circuit of the tube 9. This fact is represented by the absence of oscillations in the central part of B. When audio-frequency changes are present in the output circuit of the energy impressed upon the antenna is represented by the central part of the curve C; that is, it is an unmodulated carrier wave of radio frequency. The modulations of the carrier wave, therefore, occur in impulses.

When the energy is received upon the antenna 21 at the called station, if it is of thekind shown at the end portions of the curve C, it will produce in the out t circuit of the first detector tube 23, a current properly represented by the end portions of the curve B.

But if the energy received upon the antenna 21 corresponds to the central portion of the curve C, there will be a const the output circuit of the detector tube 23 and accordingly, no current in the secondary of transformer 24. The resulting current in the output circuit of the tube 28 is not correctly represented by the curve A, because to cor rectly represent it, the end portions of the.

or the transmission through space, usually current inindicated by the conventional antenna shown in Figs. 1 and 2, may be used.

In Fig. 3 squares have been used to represent collections of apparatus which in Figs. land 2 are shown in detail. The reference characters designating squares have each been chosen, by adding 100 to the reference character in Figs. 1 or 2 which designates a characteristic element in the collection of apparatus represented by that square. Three stations are shown in this figure,-indicated respectively by D, E, and F. The station'at which the apparatus designated by any reference character is to be found, will be in-- dicated in the following description by afiixing the letter designating the station to the numeral designating the apparatus.

The station D represents the dispatchers station and is not equipped with any switching arrangement for changing the constants of the antennae. Thesending apparatus at the dispatchers stations in permanently tuned to the frequency atwhich all the other stations are normally tuned to receive and the receiving apparatus at his station is permanently tuned to the frequency at which all the other stations are normally adjusted to send.

"A dial 63D controls the transmitting mechanism 109D so that the antenna 101D sends out a carrier wave modulated intermittently, the impulses of modulation corresponding to the impulses at the dial. This radiation is received upon each of the antennae 121 and the receiving mechanisms 125E and 125F cause the corresponding selectors 184E and 184F to be stepped. Assuming a that station E is the called station, the selector 184E will cause the bell 96E'to ring. The

. operator at station Eremoves the telephone receiver 36E from its hook, with the result that conversation'is possible between station D and station E. When the conversation is concluded, both operators hang up their rereceivers and the stations return to normal cqndition. Q v Assuming that the operator at station E wishes to call station F, he so manipulates- .the dial 63E as to cause the switching devicev 144E to change the characteristic wave lengths of the antennae lOlE'and 121E. Before this change, the antenna 121E was tuned to receive the freguency sent out from the antenna 101D an the antenna 101E was tuned to send radiations that would correspondfto the frequency for which antenna- 121]) was tuned. After this change, the frequencies characteristic of theantennae 101E and 121E are interchanged, so that these antennae are now tuned like the antennae at station D having the same reference characters. The antennae at station F are normally tuned as the antennae at station E were before this change. The result of the change is that station E is ready to send and'rece ive in the same way as the dlspatchers station and can also communicate with station vF, just as the dispatcher station would. The call is made by the dial 63E and the result of lifting the receivers 36E and 36F is the same as described in connection with the call from station D to station E.

If station F is calling station E, the operator begins by-manipulatin'g the switch 631;- which has been added to this station to illustratc the provision of a separate, manuallyoperated circuit closer for controlling the chan es in the antenna constants. The switc 631 actuates the switching device 1441* for changing the constants of the sending antenna and the switching device -14:5F for changing the constants of'the receiving antenna. wo switching devices are shown at station F, instead of the one switchingdevice 144 which is shown at station E,"in order to illustrate thatthe magnets45, 47 and 49 may be controlled directly from a circuit-closer, instead of, as illustrated in Fig. 2 having the magnet 44 control the other magnets.

. While I have shown only one embodiment of my invention in the accompanying drawing, it is capable of other modifications and changes without departing from the spiritthereof, I desire, therefore, that only such limitations'shall be placed thereon as are indicated intheprior art or in the appended claims.

I claim as my invention:

1. In a signalling-system, a first station, a remote station, transmitting apparatus at said first station including a radio frequency current generator, means for modulating the radio frequency currents from said generator, means for controlling said modulations in. accordance with a code comprising an evacuated tube, circuit connections electrically associated with said tubewhereby said tube generates current of audio frequencies, circuit connections including a microphone connected tosaid tube, whereby said tube operates as an amplifier of the currents flowing from the microphone, means including a relay for switching said tube from said first to said second connection, a receiving device at said second station including a detector, means including circuit connections for translating said audio frequencies received at said receiver from said transmitting station, means including circuitconnections for translating said code signals received from said transmitting station and means including a relay for associating either of said last two ment1oned means with said receiving device.

2. In a radio system, a telephone transmitter, a telephone receiver, a selector switch, a

carrier current modulator, a three elerfient.

tube connected thereto, means includin a relay for connecting said tube to -said se ector, means including said selector connected to said tube for transmitting code combinations code signals for operating said switch, and

means responsive to a predetermined operation of said switch for switching said receiver to said telephone receiver whereby said telephone receiver operates in accordance with receiver voicecurrents.

In testimony whereof, I have hereunto subscribed my name this 20th day of October CLARENCE A. BODDIE. 

